This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | -2 |
| 3 | 2 |
| 4 | -8 |
| 5 | 56 |
| 6 | -496 |
| 7 | 3184 |
| 8 | -22784 |
| 9 | 273920 |
| 10 | -4539136 |
| 11 | 48104704 |
| 12 | -506000384 |
| 13 | 10591523840 |
| 14 | -204528633856 |
| 15 | 2888557717504 |
| 16 | -53417657237504 |
| 17 | 1249919350046720 |
| 18 | -28453501844586496 |
| 19 | 624022403933077504 |
| 20 | -13729309300086800384 |
| 21 | 372737701735949926400 |
| 22 | -11010228423219933085696 |